1. Field of the Invention
The present invention relates to a light guide plate having V-shaped grooves and a backlight module using the same, the backlight module being typically applied in a liquid crystal display (LCD).
2. General Background
An LCD device has the advantages of portability, low power consumption, and low radiation, and has been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras and the like. Furthermore, the LCD device is considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.
A typical backlight module used in an LCD primarily includes a light source, a light guide plate, a prism sheet, and primary and secondary diffusers. The light guide plate is an important unit of the backlight module, for converting light emitting from the light source into substantially planar light. The evenness and intensity of luminance of the light guide plate are the most important optical characteristics influencing the performance of the LCD.
FIG. 9 is a schematic, side view of a typical light guide plate 90. The light guide plate 90 includes a bottom surface 91 having a plurality of V-shaped grooves 900, and a light emission surface 93. The V-shaped grooves 900 are parallel to each other, and a pitch between adjacent V-shaped grooves 900 is uniform. The heights of the V-shaped grooves 900 are the same.
FIG. 10 is a schematic, exploded side view of a backlight module using the light guide plate 90. The backlight module includes, in sequence, a first diffuser 95, a set of prism sheets 94, a second diffuser 97, the light guide plate 90, a plurality of light sources 99, and a reflector plate 96. Light beams emitting from the light source 99 enter the light guide plate 90 through the incident surface 92 in different directions. Thus, light beams reaching the V-shaped grooves 900 propagate therefrom in different directions. Some of the light beams reaching each V-shaped groove 900 are incident at the interface thereof at angles greater than a critical angle, and are reflected and then emit from the light emission surface 93. Other light beams reaching each V-shaped groove 900 are incident at the interface thereof at angles less than the critical angle, are refracted and emit from the bottom surface 91, and are then reflected by the reflector plate 96 back into the light guide plate 90. Because the V-shaped grooves 900 disposed on the light guide plate 90 have the same configuration, it is difficult to control the angles of incidence of light beams at all the interfaces such that as many light beams as possible are reflected at the interfaces. In particular, it is difficult to obtain maximum luminance of the light guide plate 90 at a center of the light emission surface 93. Thus the prism sheets 94 are generally a necessary part of the backlight module.
It is desired to provide an improved light guide plate and a backlight using the same which can overcome the above-described deficiencies including the need for prism sheets.